Cameras are commonly used in order to monitor buildings, roads, shops etc. Especially, cameras are used to monitor scenes in order to detect and/or track events in form of presence of motion.
Depending on the level of motion of the events monitored by the camera the exposure time of the image frames in a sequence of image frames in a video image stream capturing a scene monitored by the camera may be adjusted. For example according to PG Pub US2008/0043112, a long exposure time is used as long as there is no or a low level of motion in the captured scene. Whereas, when the monitored scene comprises events having a high level of motion a switch in exposure to a shorter exposure time occurs. However, a problem with this method is that when switching to the shorter exposure time the exposure time becomes too short for monitoring events having a low level of motion. It will be hard to distinguish details of the events having low level of motion, especially during dim light conditions, when the exposure time is too short. Moreover, if the detection of an event having a high level of motion fails, thus, if a long exposure time is used, the event will become blurry in the captured images.
A solution to the above is to use two or more cameras, the different cameras having different exposure time. However, such a known solution is costly and troublesome to use.